Font size in DomDistiller prefs syncs with local scaling

The font size in DomDistiller preference was linked with accessibility
scaling. Now it links with local scaling, which can also be adjusted by
pinch-to-zoom gesture. The local scaling syncs across tabs.

This local scaling doesn't sync across devices by design.

BUG=445632, 464822
TEST=browser_tests --gtest_filter="DomDistiller*"

Review URL: https://codereview.chromium.org/1225183002

Cr-Commit-Position: refs/heads/master@{#350976}
18 files changed